The least common multiple of $x$, $10$ and $14$ is $70$. What is the greatest possible value of $x$?
Answer: First, we prime factorize the given numbers: \[10=2\cdot5, \quad 14=2\cdot7, \quad 70=2\cdot5\cdot7.\]  Since the least common multiple of $10$ and $14$ is already $70$ ($2 \cdot 5 \cdot 7$), we can maximize $x$ by letting it be $\boxed{70}$.